Colored cement

ABSTRACT

AN IMPROVED PORTLAND CEMENT IS PROVIDED BY BURNING A MIXTURE OF ARGILLACEOUS AND CALCAREOUS MATERIALS WITH A COLOR-ENHANCING AMOUNT OF METAL OXIDE IN A BURNING ZONE OF A KILN AND THEREAFTER RAPIDLY QUENCHING THE RESULTING CLINKER FROM A TEMPERATURE ABOVE ABOUT 2600*F. TO EFFECT A VERY RAPID COOLING THEREOF. IT IS GENERALLY PREFERRED THAT THE CLINKER BE QUENCHED FROM A TEMPERATURE OF BETWEEN 2650*F. TO 2850*F. AT A VERY RAPID RATE SUCH AS IN A WATER QUENCH ZONE.

United States Patent O Int. Cl. C04b 7/10. US. Cl. 106-101 10 Claims ABSTRACT OF THE DISCLOSURE An improved portland cement is provided by burning a mixture of argillaceous and calcareous materials with a color-enhancing amount of metal oxide in a burning zone of a kiln and thereafter rapidly quenching the resulting clinker from a temperature above about 2600 F. to effect a very rapid cooling thereof. It is generally preferred that the clinker be quenched from a temperature of between 2650 F. to 2850 F. at a very rapid rate such as in a water quench zone.

BACKGROUND OF THE INVENTION This application is a continuation-in-part of copending patent application Ser. No. 51,361 filed June 30, 1970 now US. Pat. 3,667,976.

Prior attempts have been made to produce colored cements. These cements are and have been useful in various applications in which an aesthetic efiect is desired in the final concreteproduct made from the cement. The final product has been colored at the site at which the concrete is produced. This procedure, however, usually involves large quantities of pigments which can undesirably afiect the final properties of the concrete product. Another attempt which has been made to color cement is to grind various pigmentations with clinker as it is ground. This latter method also requires a significant amount of pigment or additive. Additionally, it does not consistently produce a good colored cement product. The latter method also results in a mere additive color, which can be bleached or eroded upon exposure, rather than one brought about by chemical interaction with the cement constituents.

For example, US. Pat. 1,958,615 discloses a method for making colored cement by which clinker or ground cement is combined with a small quantity of sulfur and heated to about 800 to 1600 F. and maintained at that temperature for several hours out of contact with oxygen. Varying colors can be obtained by heating at preselected temperatures within the range for varying lengths of time. As is evident, however, this method requires an extra processing step and an extra heating step, both of which take time and consumeadditional. energy. US.

when intermixed with the final concrete composition.

Still another method for producing colored cements is disclosed in US. Pat. 1,829,082. This patentdiscloses mixing substances such as phosphates, borates or halogen compoundsas a flux with the raw materials formaking cement and further addingto the raw materialsa metal compound such as the oxides of chromium, nickel, cobalt and copper. Specific examples are given. This disclosure states that metal complexes including borosilicates and metal sodium phosphates, for examples, produce the color tendency in the final cement product.

v Recently a technique has been discovered for producing a novel colored cement by burning raw cement materials in the presence of a color-enhancing amount of metal oxide. This technique is disclosed in my copending application Ser. No. 51,361 filed June 30, 1970, of which this present application is a continuation-in-part. The product produced by this new technique is a cement product which has a specific, durable color.

SUMMARY OF THE INVENTION According to the present invention, an improved method is provided for producing a colored cement which comprises initially burning argillaceous and calcareous materials with a sufficient amount of a metal oxide coloring agent in the burning zone of the kiln to produce a burned cement clinker and thereafter maintaining the cement clinker at a temperature above about 2600 F. prior to rapidly quenching the same. Preferably, the material passing from the burning zone in the kiln is heated by an auxiliary burner adjacent the outlet thereof to maintain the material at a temperature above about 2600 F. as it is passed to a quenching zone. Preferably, the material is rapidly quenched with Water.

DESCRIPTION OF PREFERRED EMBODIMENTS In the typical cement making process, particularly a portland cement manufacturing process, ground argillaceous materials, calcareous materials and other minor proportion reactants are mixed and fed to an elongated rotary kiln, or other reaction system including a vertical kiln or a fluid bed-type reactor or kiln. The ground argillaceous and calcareous materials are burned at temperatures ranging typically between 2600 F. and 2800 F. A chemical reaction takes place in the kiln between the argillaceous, calcareous and other retactants to produce a cement clinker primarily composed of tetracalciumaluminoferrate, tricalciumaluminate, tricalciumsilicate, and dicalciumsilicate. These products form what is called a cement clinker, which after cooling to ambient temperatures, is very finely ground with calcium sulfate to produce what is known as portland cement. The cal cium sulfate is conventionally incorporated with the ground clinker to control setting time. The argillaceous materials are typically a clay or a clay-kaolin mixture. The calcareous materials are usually the calcite found in limestone. Additionally,'other materials such iron ore, slag or other additives are ground and mixed with the raw materials fed into the kiln.

As set forth in said copending application Ser. No. 51,361, ithas been discovered that the addition of certain metals or metal compounds to the raw materials for the production of cement will produce a cement of predictable and desirable color and hue. It is to be understood that when the term metal or metal compound is used hereinafter that the metal can be in the elemental state, or can be in combined form such as an oxide or a mineral complex, or can be in ionic form. Generally, the metals can be added to the raw materials in amounts (expressed as the metal oxide) from about 0.2%, preferably about 0.3% to about 2.0% and most preferably from about 0.4% to about 0.7% based on the total dry accord with this invention. Going beyond the preferred 3 limits, for example, below the lower limit of 0.2, will produce a cement which had a significant natural' gray tone', but still slightly colored. Going above the upper limit of about 5% will produce a cement having the color characteristics of the particular metal added, however, the color additive will begin to affect the'hydraulic properties of the cement. In addition, the color and hue and tone will begin to become somewhat muddy, iie.,it will begin to have an undesirable aesthetic quality. It is to be under stood that when a percent of metal is utilized herein, it is expressed as a percentage by weight of the metal oxide, eigfl, TiO ZrO Mn O and V although the metal might be aded in elemental compound or mineral-com plex form. I

The percentage ranges expressed in the foregoing paragraph are based on total dry raw materials. These same ranges based on an analysis of cement clinker are, expressed as the oxide of the metal, from about 0.3% to about 8.0%, preferably about 0.5% to about 3.2%, and most preferably about 0.6% to about 1.0% by weight of the metal coloring agent in the final ground clinker.

The metals which have been discovered which will lend a desirable and predictable hue and color to a cement clinker are those which appear in Groups IV B, Y-B and VIIB of the Periodic Table as it appears at page B2 of the 45th edition of the Handbook of Chemistry and Physics, Chemical Rubber Publishing'Companyfof Cleveland, Ohio (1964). Preferred among these metals are titanium, zirconium, manganese and vana'dium. Addition of titanium to the raw materials will produce a cement clinker which has a buff color, that is, it will produce a yellowish hue in the final cement clinker. Addition of manganese to the raw materials will producea clinker with a definite blue tone. Addition of vanadium will produce a silver-gray bordering on a green tonefliZir- 35 conium will again produce a buff colored cement clinker;

It has been found that the color and hue'is' somewhat dependent upon the reaction or burning temperatures; For example, when titanium is mixed with raw materials, a reaction temperature of between 2500 and 2 700 F. will produce a grayish buff or grayish yellow j'c'ernent clinker. However, when the reaction temperature ranges between 2600 F. and'3000" F., a definite buff tone and very desirable hue will be present. Preferredpercentag'es of titanium to be added to the raw materials, based on the'dry weight of the raw materials, ranges between 0.3% by weight (expressed as titanium dioxide) to about 2.0% by weight. The most preferred burning zone temperatures or reaction temperatures range between about 2650" F. to 3000 F. I

Additionally, it has been found that quenching the clinker produced by adding the metals set "forth'above will additionally fix and produce a brighter hue "of the same tone as is produced by merely adding the me'tal alone. Quenching can be accomplished by an air blast 55 upon the hot clinker as it leaves the kiln, or canlbe accomplished by other quenching media suchIas steamior water. Normally, clinker will cool to ambient tempera:

ture in about 10 to more than 20 minutes. If, the clinker is quenched from its burning temperature. of ;around 2700? F. to near room temperature in abouthalf that time, that is, from 5 to 12 or so minutes, the cli ker l take on a very definite bright, aesthetically desirable hue. a

and color characteristic of the metal whichha been added. to the raw materials. As a general guideline, the desirable quality contributed by quenching wil l occur if the clinker is cooled about 1.5 or more timesfaster, than II occurs in conventional production. Generally, ,quenching in a time span of about 25% to 75% of that which the: clinker normally takes to cool to room temperature, will produce the desirable increase in hue andcolorfixation.

More specifically, and in accordance with this inven: tion, it has been found that in order to efiectively fix and produce a brighter hue of the same tone as is produced by merely adding the coloring agent alone, the clinker 'from the burning zone of the kiln should be-m'aintained at a prequench temperature above about 2600 F. at the time that the quenching operation begins. Thereafter, quenching is preferably accomplished by the methods as set forth above, and generally in the same span as set forth above. It is preferred that this prequench temperature be maintained at a point substantially above -about-. 2 I600 F., eg, up to about' 3000" F. Considering product quality as well as economicand engir'ieering lfactors, the preferred prequench. temperature is in the range of 2650 to 2850 F.

This prequench temperature can be maintained in any convenient manner.-It is'only ne'cessary that the clinker passing from the burning zone of the kiln be maintained above about 2600 F. at the time that the rapid quench ing process begins. It has been found, for example, that when using conventional rotary .kilns for producing Type E Icements that the ,clinker has a tendency to cool to a temperature below about 2600 F; before it is quenched. As a result, it has beenvery difiicult to produce cements ofsome of the more desirable, brighter hues. Thus, it has been found that the, positioning of an auxiliary burner adjacent, the outlet of suchkilns will satisfactorily main tain ,theclinker from the. burning zone at a temperature well. above 2600 Subsequent rapid quenching as de scribed above, will satisfactorily produce cement of, the

brighter hues.

It is not completely understood why a temperature of about 2600 F. or higher of the clinker entering the rapid quenching zone ,is necessary to produce cements having improved colors which are very bright and intense.--It is believed that the components of the cement clinker are basically ina solid solution state at temperatures above 2600 'F-. and they begin their normal process of crystallization at about 2600" F. Therefore, one theory is thata rapid quenching ofthe clinker while it is maintained in the general state ofsolid solution, results in rapid crystallization of the materials directlyfrom the solid solution state" to yield a resulting crystalline structure having a color* -which" is brighter and' -'more intense :than that oht'ained by quenching-from'a lower temperature.

I I I EXAMPLES. I

The following examplesare presented as guidelines for those of ordinary skilljinthe artto reproduce the pres-v e'r'it invention. Included amongthe'examples are preferred embodimentsof the invention. These examples are intended as exemplifications only and are not intended to be delimitative of the invention in any manner; All perc'en'ta'ges usedftherein are by weight unless otherwise statediAll formulations in the following examples are intended toprp'ducea fType I general purpose ortland cement which has t-he 'color, tone and hue characteristic of the metal which has been added, although the coloring me 'anism"will be equally effective with other' cement Example cement'raw material" mix of the following chemical co position ispre'pared using a mixture of limestone, clay The foregoing mixture'is altered by varying the addition of limestone and ilmenite. -(Ilmenitev is a mineral complex of the formula TiO -FeO. The ilmenite utilized in this par- TABLE II.RAW MIXES WITH Tl VARIED As can be seen from the foregoing data, when the burning temperature reaches a point below 2600- F., the clinker retains some of its-natural gray tone. When the temperature is above 2600 F., a good quality bufl? clinker brodudl. A

Samples (weight percent) Composition SiO,z 14. 14. 0 14. 0 13. 9 13. 8 14. 0 l3. 7

A120 3.6 3.6 3.6 3.6 3.6 3.5 I 3.5 F8203. 1. 7 1. 7 1. 7 1. 7 1. 7 1. 7 1. 7 ,CaO. ..j.. 41. 2 41. 2 41. 1 41. 0 41. 4 41. 0 4111' LOSS on Ignition. 37. 0 37. 0 37. 0 36. 36. 7 37. 1 37. 0 Composition: T102 0. 0 0. 1 0. 5 0. 75 1. 0 2. 0 3. O

I About 100 grams of each of the raw mixes is pellitized. 20 gram portions from each of these 100 gram samples are separately burned in an electric furnace for 20 minutes at temperatures varying from 2500 F. to 3000 F. After burning for 20 minutes, the samples are removed at once from the furnace and allowed to cool by normal radiation and convection to room temperature. The samples are ground with mortar and pestle and visually compared for color. The results are set forth in Table III, using the following color code: G, gray; GY, gray with yellow trace; B, good buff hue; B/ M, buff tone which is slightly muddy.

TABLE III.COLOR RESULTS FROM EXAMPLE I Samplenumber G GY GY GY GY GY GY G GY GY GY GY GY GY G GY B B B B/M B/M G GY B B B B/M B/M G GY B B B B/M B/M G GY B B B B/M B/M G GY B B B B/M B/M Theprocedure of Example I is repeated using rutile and purified titanium dioxide, rather than ilmenite. The results are substantially the same.

Example 11 A cement raw mix weighing 175 pounds was prepared using a mixture of limestone, clay, iron ore and ilmenite ore; The chemical composition of the cement raw mix is.

set forth in Table IV.

TABLE IV Cement raw mix for Example II The raw mix is pellitized and burned in a 5" x 14" x long laboratory rotary kiln. Samples of the clinker are taken and visually checked for color. The color is recorded'at '30 minute intervals. In addition, the temperature of "the kiln burning zone is taken and recorded at one hour intervals. The run was continued for about 7 hours. The results are set forth in Table V.

TABLE V.COLOR RESULTS OF EXAMPLE II Clinker Production Temperature rate, leaving burnlhr. ing zone, F. Color 2,700 Bufi. 2,630 Do. 2,590 Yello -gray. 2,640 Bufi.

2,640 Do. 2,645 Do. 2,620 Do.

t ar-t mmh a a: were TABLE VL-RAW MIX ANALYSES, EXAMPLE Ill Sample (weight percent) Ignition loss Composition:

Each of the three samples are pelletized and burned in an electric furnace for about 20 minutes at 2750 F. Im-v mediately after the burn, the clinker samples thus formed are removed from the furnace and allowed to cool by natural convection and radiation to room temperature. The clinker is then ground with a mortar and pestle. The sample 1 to which manganese is added has a definite blue tone. The sample to which vanadium is added has a silver.- gray to green tone. The sample to which zirconium is added has a definite buif color comparable to that obtained above with titanium.

Example IV Five samples of a cement raw mix weighing'aboutlOO pounds are prepared using a mixture of limestone, clay, iron ore, and ilmenite ore. The five samples are individually pelletized and burned in a 5" x 14" x 10' long laboratory rotary kiln. Immediately upon being discharged from the kiln, the clinker is quenched in water. Thereafter, the clinker is dried and ground. Clinker analyses for the five samples are set forth in Table VII.

TABLE VIL-CLINKER ANALYSIS FOR EXAMPLE V Sample number (percent by weight) Composition:

The color of the ground clinker with varying percentages of titanium in the clinker is set forth in Table VIII.

TABLE VIIL-COLOR OF GROUND CLINKER As is observed, the color obtained is yellowish and with TiO content of 0.5% by weight and, above the color obtained is definitely a yellow to buff tone. The color obtained upon quenching is brighter and more intense than that obtained when the clinker is cooled to room temperature in a laboratory tray exposed to the atmosphere.

From the foregoing examples, it can be seen that the addition of metals to a raw cement mix will give a definite color to the final clinker. It can also be seen that the color is characteristic of the particular metallic element or compound which is added to the raw mix. It is to be understood that the metal, whether elemental, an oxide or a mineral complex, can be added to the kiln with the raw material feed end or to the burning zone, for example, by insufflation. The metal can also be added intermediate the feed end and the burning zone by a suitable mechanism, for example, a scoop feeder, or if desired at any point upstream of the feed end, including during initial grinding of reactant materials or into a preheating system.

The role which the metals assume to provide color in the cement composition is not completely understood. One theory is that, for example, the titanium is in some way combined with the ferrite phase of the clinker and that the aluminate/ferrite molar ratio must be greater than one in order to give the clinker a butt color. For example, if no titanium is present in the cement raw mix and the final clinker has an aluminate to ferrite ratio less than one, the color of the clinker is gray. The clinker is white if the ferrite phase is not present and if titanium is present. The color, however, returns to gray when the ferrite phase is present and the aluminate to ferrite phase is less than one. When, however, the titanium is present and the aluminateferrite ratio is greater than one, the color of the cement clinker becomes buff. It is, therefore, believed that the color tendency is somehow interrelated and connected with the ferrite phase. Therefore, if the aluminate to ferrite ratio is greater than one in the presence of a metal, the cement clinker will exhibit the characteristic color and hueof the particular metal.

Example VI A Type I portland cement raw mix was prepared using a mixture of limestone, clay, iron ore and ilmenite ore. The ilmenite ore was incorporated into the mix in a ratio of three pounds per barrel (approx. 600 lbs.) raw material.

About 3500 barrels of the raw mix was burned in a conventional Type I portland cement kiln. The kiln included a 20 foot length at the outlet end thereof extending from the internal burning zone, and sixteen portholes were positioned around the periphery of the kiln at a point approximately 10 feet from the end of the burning zone. The clinker was in the burning zone for a period of from about 12 to minutes and was burned at a temperature between 2700 F. and 2800 F. The clinked passing from the burning zone was discharged from the rotating kiln through the portholes and into water quench zones. The clinker was rapidly quenched from temperatures no higher than 2600 F. The resulting material, while definitely bufi colored had a very muddy tone.

Next, an annular refractory brick dam was positioned about the inside periphery of the kiln, just downstream of the portholes. Furthermore, an auxiliary burner (using natural gas as a fuel) was positioned within the outlet end of the kiln so that the lower portion of its flame contacted the brick dam and the top surface'of the load passing through the kiln. Again, the quench zone operatively communicated with the portholes of the kiln. The above twenty-four hour run was duplicated using the same raw materials but in the modified kiln wherein the auxiliary flame was utilized to maintain the material from the burning zone through the portholes at a temperature of about 2650 F. The material 'was immediately and rapidly quenched from this temperature within the water quench zone. This procedure resulted in buif colored cement having a color which was very much brighter and more intense than that obtained when the clinker was quenched in the run above.

The utility of the foregoing invention is apparent to those of ordinary skill in the art. Its utility is especially apparent to those in the business of manufacturing portland cement due to the large demand for cements of buff and other colors. Although the foregoing specification has set forth this invention in relation to preferred embodiments, other. variations, alterations and equivalent formulations and compositions will be apparent to those of ordinary skill. The invention is not intended to be limited in any manner by the foregoing description except as defined by the appended claims.

What is claimed is:

1. In a method of producing a colored portland cement which includes burning in a burning zone of a kiln finely divided argillaceous and calcareous reactant materials together with from 0.2 to 5 weight percent thereof of an oxide of a metal selected from Groups IV-B, V-B and VII-B of the Periodic Table, and then rapidly quenching the clinker after it has been burned, the improvement comprising:

rapidly quenching said clinker from a temperature above about 2600 F.

2. The method of claim 1 wherein said clinker is quenched with water.

3. The method of claim 1 wherein said clinker is rapidly quenched from a temperature in the range of from about 2650 F. to about 2850 F. I

4. The method of claim 1 wherein said quenching occurs at the rate of at least about 1.5, times the normal cooling rate.

5. The method of claim 1 wherein said clinker is quenched from said temperature of above about 2600 F. to a temperature of about 500 F. in less than about 10' minutes.

6. The cement composition produced by the method of claim 1.

7. The method of claim 1 wherein said metal oxide is an oxide of a metal selected from vanadium, zirconium, manganese and titanium. v

8. The cement composition produced by the method of claim 7. v

9. The method of claim 1 wherein said metal oxide is TiOg.

10. The cement composition produced by the method of claim 9.

References Cited UNITED STATES PATENTS 1,562,207 11/1925 Croll 106-l02 3,667,976 6/1972 Tanner 106-101 JAMES E. POER, Primary Examiner 

